Dialysis Systems and Methods

ABSTRACT

This invention relates to dialysis systems and methods. In some implementations, a method includes applying vacuum pressure to a device of a dialysis system, and then determining, based on a detected fluid level or measured pressure, whether the device is functioning properly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority under 35 U.S.C.§120 to U.S. Ser. No. 13/520,082, filed Sep. 18, 2012, which is a 371 ofInternational Application No. Application No. PCT/US2011/020537, filedon Jan. 7, 2011, which is a continuation-in-part of U.S. Ser. No.12/683,980, filed Jan. 7, 2010. The contents of these priorityapplications are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

This invention relates to dialysis systems and methods.

BACKGROUND

Dialysis is a treatment used to support a patient with insufficientrenal function. The two principal dialysis methods are hemodialysis andperitoneal dialysis.

During hemodialysis (“HD”), the patient's blood is passed through adialyzer of a dialysis machine while also passing a dialysis solution ordialysate through the dialyzer. A semi-permeable membrane in thedialyzer separates the blood from the dialysate within the dialyzer andallows diffusion and osmosis exchanges to take place between thedialysate and the blood stream. These exchanges across the membraneresult in the removal of waste products, including solutes like urea andcreatinine, from the blood. These exchanges also regulate the levels ofother substances, such as sodium and water, in the blood. In this way,the dialysis machine acts as an artificial kidney for cleansing theblood.

During peritoneal dialysis (“PD”), a patient's peritoneal cavity isperiodically infused with dialysis solution or dialysate. The membranouslining of the patient's peritoneum acts as a natural semi-permeablemembrane that allows diffusion and osmosis exchanges to take placebetween the solution and the blood stream. These exchanges across thepatient's peritoneum, like the continuous exchange across the dialyzerin HD, result in the removal waste products, including solutes like ureaand creatinine, from the blood, and regulate the levels of othersubstances, such as sodium and water, in the blood.

Many PD machines are designed to automatically infuse, dwell, and draindialysate to and from the patient's peritoneal cavity. The treatmenttypically lasts for several hours, often beginning with an initial draincycle to empty the peritoneal cavity of used or spent dialysate. Thesequence then proceeds through the succession of fill, dwell, and drainphases that follow one after the other. Each phase is called a cycle.

SUMMARY

In one aspect of the invention, a method includes applying vacuumpressure to an air release device of a dialysis system. The air releasedevice includes a vent. After applying the vacuum pressure to the airrelease device, a fluid level within the air release device is detected.Based on the fluid level within the air release device, it is determinedwhether the air release device is functioning properly.

In another aspect of the invention, a method includes applying vacuumpressure to a device of a dialysis system. The device includes a vent.After applying the vacuum pressure to the device, a pressure within afluid line that is fluidly connected to the device is measured. Based onthe measured pressure, it is determined whether the device isfunctioning properly.

In a further aspect of the invention, a method includes applying vacuumpressure to an air release device of a dialysis system. The air releasedevice includes a vent. After applying the vacuum pressure to the airrelease device, a fluid level within the air release device is detected,and if the fluid level within the air release device exceeds a givenlevel after applying the vacuum pressure to the air release device, auser is informed that the air release device is not functioningproperly.

In an additional aspect of the invention, a method includes applyingvacuum pressure to a device of a dialysis system. The device includes avent. After applying the vacuum pressure to the device, a pressurewithin a fluid line that is fluidly connected to the device is measured,and if the measured pressure is less than a certain pressure, a user isinformed that the device is not functioning properly.

In yet another aspect of the invention, a dialysis system includes anair release device with a vent, a level detector configured to detect alevel of fluid within the air release device, and a control unitconnected to the level detector. The control unit is configured todetermine whether the air release device is functioning properly basedon a detected fluid level within the air release device when vacuumpressure is applied to the air release device.

In a further aspect of the invention, a dialysis system includes adevice with a vent, a fluid line fluidly connected to the device, apressure sensor configured to measure pressure of fluid within the fluidline, and a control unit connected to the pressure sensor. The controlunit is configured to determine whether the device is functioningproperly based on a measured pressure of fluid within the fluid linewhen vacuum pressure is applied to the device.

Implementations can include one or more of the following features.

In some implementations, determining whether the air release device isfunctioning properly includes determining whether the vent of the airrelease device is functioning properly.

In certain implementations, the fluid level within the air releasedevice is detected by a level detector of the dialysis system, and thelevel detector is positioned adjacent the air release device.

In some implementations, the level detector includes a transmitterconfigured to emit ultrasonic signals and a receiver adapted to receiveultrasonic signals.

In certain implementations, the level detector is connected to a controlunit of the dialysis system in a manner such that signals related to thedetected fluid level can be transmitted to the control unit.

In some implementations, applying vacuum pressure to the air releasedevice includes closing off lines upstream and downstream of the airrelease device and activating a pump to draw fluid out of the airrelease device.

In certain implementations, closing off the line upstream of the airrelease device includes turning off a pump configured to circulate fluidthrough the air release device, and closing off the line downstream ofthe air release device includes clamping the line downstream of the airrelease device.

In some implementations, the pump that is activated to draw fluid out ofthe air release device is an ultrafiltration pump.

In certain implementations, the method further includes misbalancing abalancing chamber that is in fluid communication with the air releasedevice to draw the fluid out of the air release device.

In some implementations, applying vacuum pressure to the air releasedevice includes closing off lines upstream and downstream of the airrelease device and activating a pump to draw fluid out of the airrelease device.

In certain implementations, the dialysis system includes first andsecond lines connected to the air release device and a pump configuredto circulate fluid from the first line to the air release device to thesecond line during dialysis treatment, and applying vacuum pressure tothe air release device includes closing off the second line andoperating the pump in a manner to circulate fluid from the second lineto the air release device to the first line.

In some implementations, the method further includes indicating to auser that the air release device is not functioning properly if, basedon the fluid level within the air release device, it is determined thatthe air release device is not functioning properly.

In certain implementations, indicating to the user that the air releasedevice is not functioning properly includes emitting a visual signal.

In some implementations, indicating to the user that the air releasedevice is not functioning properly includes emitting an audio signal.

In certain implementations, indicating to the user that the air releasedevice is not functioning properly includes disabling one or morefunctions of the dialysis system.

In some implementations, the method further includes applying positivepressure to the air release device after applying the vacuum pressuresuch that air drawn into the air release device by the vacuum pressureis forced out of the air release device by the positive pressure.

In certain implementations, the dialysis system is a hemodialysissystem.

In some implementations, the method is performed during hemodialysistreatment.

In certain implementations, the method is performed before hemodialysistreatment.

In some implementations, the fluid within the air release deviceincludes saline.

In certain implementations, the fluid within the air release deviceincludes blood.

In some implementations, the air release device includes a drip chamberand a pressure sensor assembly extending from the drip chamber, and thepressure sensor assembly includes a transducer protector that houses thevent.

In certain implementations, determining whether the air release deviceis functioning properly includes determining whether the vent of thetransducer protector is functioning properly.

In some implementations, detecting the fluid level within the airrelease device includes detecting a fluid level within the drip chamber.

In certain implementations, the measured pressure is transmitted in theform of a signal to a control unit of the dialysis system.

In some implementations, the control unit is a microprocessor.

In certain implementations, the pressure is measured by a pressuresensor of the dialysis system.

In some implementations, the pressure sensor includes a pressuretransducer.

In certain implementations, the pressure sensor is attached to adialysis machine of the dialysis system and is aligned with the fluidline.

In some implementations, the vacuum pressure is applied to the airrelease device by activating a pump.

In certain implementations, the line is in fluid communication with adialyzer, a dialysate line is in fluid communication with the dialyzer,and the pump is an ultrafiltrate pump that is fluidly connected to thedialysate line.

In some implementations, the pump is a drug pump that is configured tointroduce fluid into the fluid line when operated in a first directionand is configured to draw fluid out of the fluid line when operated in asecond direction.

In certain implementations, applying the vacuum pressure includesoperating the drug pump in the second direction.

In some implementations, applying vacuum pressure to the device includesclosing off lines upstream and downstream of the device and activating afirst pump in fluid communication with a portion of the lines betweenlocations where the lines are closed off.

In certain implementations, closing off the line upstream of the deviceincludes turning off a second pump configured to circulate fluid throughthe lines, and closing off the line downstream of the air release deviceincludes clamping the line downstream of the device.

In some implementations, the first pump is an ultrafiltration pump.

In certain implementations, the method further includes misbalancing abalancing chamber that is in fluid communication with the device toapply vacuum pressure to the device.

In some implementations, the dialysis system includes first and secondlines connected to the device and a pump configured to circulate fluidfrom the first line to the device to the second line during dialysistreatment, and wherein applying vacuum pressure to the device includesclosing off the second line and operating the pump in a manner tocirculate fluid from the second line to the device to the first line.

In certain implementations, the device is determined to be functioningimproperly if the measured pressure is less than a desired pressure.

In some implementations, the method further includes indicating to auser that the device is not functioning properly if the measuredpressure is less than the desired pressure.

In certain implementations, the method further includes applyingpositive pressure to the device after applying the vacuum pressure suchthat air drawn into the device by the vacuum pressure is forced out ofthe device by the positive pressure.

In some implementations, the device includes an air release device.

In certain implementations, the device includes a pressure transducerprotector.

Implementations can include one or more of the following advantages.

In some implementations, the device (e.g., the air release device) istested before treatment begins. As a result, if the device is determinedto be functioning improperly, the operator of the system can replace orrepair the device prior to treatment such that treatment is notinterrupted. Testing the device prior to treatment (e.g., during primingof the dialysis system) also helps to ensure that the operator of thedialysis system is present to promptly replace or repair the device. Forexample, in many clinical settings, the operator of the dialysis systemtends to walk away from the system after the automated portion of thetreatment begins. Thus, in such clinical settings, testing the deviceprior to treatment helps to ensure that the operator of the system isaround to correct any identified problem with the device.

In certain implementations, the device (e.g., air release device) isperiodically tested during treatment. As a result, damage occurring tothe device during treatment can be detected. In the case of an airrelease device, for example, this technique can be used to detectwhether the vent of the air release device has become clogged, which cannegatively affect the ability of the vent to vent air or other gasesfrom the air release device to the atmosphere. If the device isdetermined to be functioning improperly, the operator can quickly takemeasures to help ensure that treatment is not negatively affected by themalfunctioning device. For example, in implementation in which thedevice is an air release device of a hemodialysis system, the user canavoid the introduction of additional fluids (e.g., drugs) that mightcontain air or other gases into the blood circuit, or the user cantemporarily stop the treatment and replace or repair the air releasedevice. This can help to ensure that air is not introduced into thepatient during treatment.

In some implementations, the testing of the device (e.g., the airrelease device) is automated. As a result, the operator of the systemcan identify whether the device is functioning improperly with littleeffort. This helps to ensure that the operator of the system does notoverlook a defective or otherwise malfunctioning device.

In certain implementations, certain functions of the dialysis system aredisabled upon determining that the device (e.g., the air release device)is not functioning properly. The disabled functions can, for example, befunctions required to perform treatment such that treatment cannot beperformed until the malfunctioning device has been repaired or replaced.In some implementations, for example, a pump of the machine can bedisabled to prevent the machine from circulating fluid until the devicehas been replaced or repaired. This helps to ensure that the treatmentof the patient is not negatively affected by the malfunctioning device.

Other aspects, features, and advantages will be apparent from thedescription, drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a front perspective view of a hemodialysis system.

FIG. 2 is a front perspective view of the hemodialysis system of FIG. 1with a door of a module of the hemodialysis system in an open positionto expose a blood component set secured to the module.

FIG. 3 is a front view of the blood component set of the hemodialysissystem of FIGS. 1 and 2.

FIG. 4 is a rear view of the blood component set of the hemodialysissystem of FIGS. 1 and 2.

FIG. 5 is a front view of an air release device of the blood componentset of FIGS. 3 and 4.

FIG. 6 is a top view of the air release device of FIG. 5.

FIG. 7 is a bottom view of the air release device of FIG. 5.

FIG. 8 is a top perspective view of the air release device of FIG. 5,with the air release device lying horizontally on its rear surface.

FIG. 9 is a front view of the hemodialysis system of FIG. 1 with thedoor of the module of the system in an open position and the bloodcomponent set removed from the module to expose blood pumping andmonitoring instruments on the front face of the module.

FIG. 10 is a schematic of fluid flow through the blood circuit anddialysate circuit of the hemodialysis system of FIG. 1.

FIG. 11 is a schematic of fluid flow through the blood circuit anddialysate circuit of the hemodialysis system of FIG. 1 when thehemodialysis system is connected to a patient for treatment.

FIG. 12 is a schematic of a hemodialysis system including a bloodcomponent set with a pressure sensing blood line having a transducerprotector connected to a pressure transducer of a hemodialysis machine.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a hemodialysis system 100 includes ahemodialysis machine 102 to which a disposable blood component set 104that forms a blood circuit is connected. During hemodialysis, arterialand venous patient lines 106, 108 of the blood component set 104 areconnected to a patient and blood is circulated through various bloodlines and components, including a dialyzer 110, of the blood componentset 104. At the same time, dialysate is circulated through a dialysatecircuit formed by the dialyzer 110 and various other dialysatecomponents and dialysate lines connected to the hemodialysis machine102. Many of these dialysate components and dialysate lines are locatedinside the housing of the hemodialysis machine 102, and are thus notvisible in FIGS. 1 and 2. The dialysate passes through the dialyzer 110along with the blood. The blood and dialysate passing through thedialyzer 110 are separated from one another by a semi-permeablestructure (e.g., a semi-permeable membrane and/or semi-permeablemicrotubes) of the dialyzer 110. As a result of this arrangement, toxinsare removed from the patient's blood and collected in the dialysate. Thefiltered blood exiting the dialyzer 110 is returned to the patient. Thedialysate that exits the dialyzer 110 includes toxins removed from theblood and is commonly referred to as “spent dialysate.” The spentdialysate is routed from the dialyzer 110 to a drain.

One of the components of the blood component set 104 is an air releasedevice 112. The air release device 112 includes a self-sealing ventassembly 114 (shown in FIG. 5) that allows air to pass therethroughwhile inhibiting (e.g., preventing) liquid from passing therethrough. Asa result, if blood passing through the blood circuit during treatmentcontains air, the air will be vented to atmosphere as the blood passesthrough the air release device 112. The air release device 112 can betested prior to or during treatment to ensure that it is functioningproperly. To test the air release device 112, a vacuum is applied to achamber 116 (shown in FIG. 5) of the air release device 112 and theliquid level (e.g., saline level or blood level) within the chamber 116of the air release device 112 and/or the pressure within a portion ofthe blood circuit including the air release device 112 is monitored. If,in response to the applied vacuum, the liquid level in the chamber 116of the air release device 112 does not substantially drop and/or thepressure in the portion of the blood circuit including the air releasedevice 112 falls below a certain value, this indicates that aninsufficient amount of air is entering the release device 112, whichfurther indicates that the vent assembly 114 of the air release device112 is likely blocked. In response, the operator can replace or repairthe improperly functioning air release device 112 or the entire bloodcomponent set 104 of which the air release device 112 is a part. Thishelps to ensure that any air within the blood circuit during treatmentis allowed to escape to atmosphere before reaching the patient. Methodsof testing the air release device 112 will be described in greaterdetail below.

Still referring to FIGS. 1 and 2, the hemodialysis machine 102 includesa touch screen 118 and a control panel 120. The touch screen 118 and thecontrol panel 120 allow the operator to input various differenttreatment parameters to the hemodialysis machine 102 and to otherwisecontrol the hemodialysis machine 102. In addition, the touch screen 118serves as a display to convey information to the operator of thehemodialysis system 100. A speaker 122 is positioned below the touchscreen 118 and functions to provide audio signals to the operator of thesystem 100. Thus, the hemodialysis machine 102 is capable of providingboth visual alerts via the touch screen 118 and audio alerts via thespeaker 122 to the operator of the system 100 during use. While thespeaker 122 has been described as being positioned below the touchscreen 118, it should be appreciated that the speaker 122 could bepositioned at any of various other locations on the hemodialysis machine102.

As shown in FIGS. 1 and 2, a dialysate container 124 is connected to thehemodialysis machine 102 via a dialysate supply line 126. A drain line128 and an ultrafiltration line 129 also extend from the hemodialysismachine 102. The dialysate supply line 126, the drain line 128, and theultrafiltration line 129 are fluidly connected to the various dialysatecomponents and dialysate lines inside the housing of the hemodialysismachine 102 that form part of the dialysate circuit. Duringhemodialysis, the dialysate supply line 126 carries fresh dialysate fromthe dialysate container 124 to the portion of the dialysate circuitlocated inside the hemodialysis machine 102. As noted above, the freshdialysate is circulated through various dialysate lines and dialysatecomponents, including the dialyzer 110, that form the dialysate circuit.As the dialysate passes through the dialyzer 110, it collects toxinsfrom the patient's blood. The resulting spent dialysate is carried fromthe dialysate circuit to a drain via the drain line 128. Whenultrafiltration is performed during treatment, a combination of thespent dialysate and excess fluid drawn from the patient is carried tothe drain via the ultrafiltration line 129.

The blood component set 104 is secured to a module 130 attached to thefront of the hemodialysis machine 102. The module 130 includes a bloodpump 132 capable of driving blood through the blood circuit. The module130 also includes various other instruments capable of monitoring theblood flowing through the blood circuit. The module 130 includes a door131 that when closed, as shown in FIG. 1, cooperates with the front faceof the module 130 to form a compartment sized and shaped to receive theblood component set 104. In the closed position, the door 131 pressescertain blood components of the blood component set 104 againstcorresponding instruments exposed on the front face of the module 130.As will be described in greater detail below, this arrangementfacilitates control of the flow of blood through the blood circuit andmonitoring of the blood flowing through the blood circuit.

FIGS. 3 and 4 are front and back views, respectively, of the bloodcomponent set 104. As shown in FIGS. 3 and 4, the blood component set104 includes various different blood lines and blood components,including the air release device 112, that are secured to a carrier body134. The carrier body 134 forms a series of apertures and recesses forcapturing and retaining the various blood lines and components. Thecarrier body 134 includes a recessed portion (shown on the left side ofFIG. 3 and the right side of FIG. 4) and a flat portion (shown on theright side of FIG. 3 and the left side of FIG. 4). The recessed portionis configured to retain most of the blood components while the flatportion is configured to hold the dialyzer 110. As shown in FIG. 4,projections 135 extend from the rear surface of the carrier body 134.These projections 135 cooperate with recessed regions formed in thefront face of the module 130 to secure the carrier body 134 and thus theblood component set 104 to the module 130. The projections 135 also helpto properly align the blood component set 104 with the front face of themodule 130 such that the various blood components and blood lines of theblood component set 104 operatively mate with associated instruments onthe front face of the module 130 when the blood component set 104 issecured to the module 130 and the door 131 of the module 130 is closed.

The air release device 112 is retained in an aperture formed in thecarrier body 134. The air release device 112 can, for example, besnapped into the aperture formed in the carrier body 134. In someimplementations, fingers extending from the carrier body 134 extend partway around the air release device 112 to retain the air release device112 securely to the carrier body 134. The air release device 112, asnoted above, allows gas, such as air, to escape from blood in the bloodcircuit and out of the chamber 116 of the air release device 112 throughthe vent assembly 114 positioned at the top of the chamber 116.

Referring to FIGS. 5-8, which illustrate various different views of theair release device 112, the air release device 112 has a housing 136that forms the air release chamber 116. The chamber 116 has a bottomregion 138 and a top region 140. An entry port 142 and an exit port 144are formed in a bottom surface of the housing 136. A filter 145 ispositioned at the exit port 144. The filter 145 inhibits (e.g.,prevents) blood clots in the chamber 116 from exiting the air releasedevice 112. A dam 146 extends upward from the bottom surface or floor ofthe housing between the ports 142, 144 so that all fluid entering theentry port 142 flows over the dam 146 before flowing out the exit port144.

The self-sealing vent assembly 114 of the air release device 112 islocated at the top of the housing 136. The vent assembly 114 is designedto permit air to escape from the chamber 116 while inhibiting (e.g.,preventing) liquid from escaping from the chamber 116. The vent assembly114 includes a micro-porous membrane 148 and a vent structure 150. Themicro-porous membrane 148 allows gas (e.g., from air bubbles in theblood or other circulating liquids) to vent from the chamber 116 to theatmosphere. At the same time, pores in the micro-porous membrane 148 aresmall enough to keep foreign particles and organisms from entering thechamber 116 from the outside air. In some implementations, the membrane148 includes a hydrophobic material, such as polytetrafluoroethylene(PTFE) (e.g., expanded polytetrafluoroethylene (ePTFE)). In certainimplementations, the membrane 148 is a fibrous carrier with a matted andwoven layer on top of which ePTFE or other micro-porous material isapplied. The hydrophobic micro-porous membrane 148 keeps liquid fromleaking out of the chamber 116 when the chamber 116 is substantiallyfilled with liquid and allows air to pass therethrough. The membrane 148has an average pore size of about 0.05 microns to about 0.45 microns(e.g., about 0.22 microns, about 0.2 microns). Suitable membranes areavailable from Pall Corporation, East Hills, N.Y., under the Versapor®mark and from W. L. Gore & Associates, Inc., Newark, Del.

The vent structure 150 automatically seals shut if it gets wet. As aresult, the vent structure 150 can prevent blood from escaping from thechamber 116 or other liquids from entering the chamber 116 in the eventof the membrane 148 rupturing. In some implementations, the ventstructure 150 is a solid porous block, having an average pore size ofabout 15 micron to about 45 microns, that allows air to pass through andescape from the chamber. In certain implementations, the vent structure150 is formed of a blend of polyethylene (e.g., high densitypolyethylene (HDPE)) and carboxymethylcellulose (CMC), a blend ofpolystyrene and methyl-ethyl-cellulose or of polypropylene- orpolyethylene-based porous material. Such materials are available fromPorex Corporation, Fairburn, Ga. One such product contains 90% by weightpolyethylene and -10% by weight carboxymethylcellulose with an averagepore size of about 30 microns to about 40 microns. However, otherpercentages of the materials can be used, as well as other materials andother pore sizes. For example, the vent structure 150 can include about80% to about 95% by weight high density polyethylene and about 5% toabout 20% by weight carboxymethylcellulose.

When the vent structure 150 comes into contact with liquid, the swellingagent (e.g., cellulose component, such as carboxymethylcellulose) of thevent structure expands, thereby closing off the pores in the polymercomponent (e.g., high density polyethylene) of the vent structure 150.The vent structure 150 is mounted adjacent to and just above themembrane 148 so that the membrane 148 is located between the ventstructure 150 and the chamber 116. The vent structure 150 inhibits(e.g., prevents) condensation from accumulating on and contacting themembrane 148. For example, if condensation begins to build up on thevent structure 150, the pores of the vent structure close therebyinhibiting the condensation from reaching the membrane 148. The ventstructure 150 similarly inhibits (e.g., prevents) liquid from escapingfrom the chamber 116. If, for example, the membrane 148 were to ruptureand liquid were to pass through the ruptured membrane 148, the pores ofthe vent structure 150 would automatically close upon coming intocontact with the liquid.

When the chamber 116 of the air release device 112 contains blood,inhibiting (e.g., preventing) the protein in the blood from accumulatingon the membrane 148 can maintain the hydrophobic characteristic of themembrane 148. Whole blood can be kept from the membrane 148 by providingsaline between the blood and the membrane 148. The height and shape ofthe chamber 116 are sufficient to maintain a blood/saline interface 152,and thus inhibits (e.g., prevents) the saline above the interface 152from substantially mixing with blood below the interface 152.

Suitable air release devices are described in greater detail in U.S.Patent Application Publication No. 2009/0071911, entitled “Safety VentStructure for Extracorporeal Circuit,” which is incorporated byreference herein.

Referring back to FIGS. 3 and 4, arterial and venous pressure sensorcapsules 154, 156 are also positioned in apertures formed in the carrierbody 134 of the blood component set 104. Each of the pressure sensorcapsules 154, 156, as shown in FIG. 4, includes an annular rigid member155, 157 to which a thin membrane 159, 161 is secured. The annular rigidmembers 155, 157 and the thin membranes 159, 161 of the capsules 154,156 together form a pressure sensor chamber through which blood flowsduring use. When the blood component set 104 is secured to the frontface of the module 130 of the hemodialysis machine 102, the thinmembranes 159, 161 of the pressure sensor capsules 154, 156 face thefront face of the module 130. The pressure within the pressure sensorchambers can be detected through the thin membranes 159, 161 by pressuresensors (e.g., a pressure transducers) on the front face of the module130 during use. Suitable capsules are described further in U.S. Pat. No.5,614,677, “Diaphragm Gage for Measuring the Pressure of a Fluid,” whichis incorporated herein by reference.

The arterial patient line 106, as shown in FIGS. 3 and 4, is containedwithin a recess formed in the carrier body 134. One end of the arterialpatient line 106 is fluidly connected to an artery of a patient duringtreatment. The arterial patient line 106 is also fluidly connected tothe pressure sensor capsule 154. The arterial patient line 106 extendsalong the recess to a first pump line adaptor 158, which connects thearterial patient line 106 to one end of a U-shaped pump line 160. Theother end of the pump line 160 is connected to a second pump lineadaptor 162, which is fluidly connected to a dialyzer inlet line 164.The dialyzer inlet line 164 is connected via a tube adaptor to a bloodentry port 166 of the dialyzer 110. A blood exit port 168 of thedialyzer 110 is connected to another tube adaptor, which connects thedialyzer 110 to a dialyzer outlet line 170. The pressure sensor capsule156 is positioned along the dialyzer outlet line 170, upstream of theair release device 112. The pressure sensor capsule 156 is fluidlyconnected to the entry port 142 (shown in FIG. 5) of the air releasedevice 112. The pressure sensor capsule 156 allows blood pressure on thevenous side of the dialyzer 110 to be sensed by a mating pressure sensoron the front face of the module 130 during treatment. The venous patientline 108 is connected to the exit port 144 (shown in FIG. 5) of the airrelease device 112. The venous patient line 108 extends from the airrelease device 112 and is fluidly connected to a vein of a patientduring treatment.

Still referring to FIGS. 3 and 4, in addition to the blood lines formingthe main blood circuit described above, a saline delivery line 172 and adrug delivery line 174 are connected to the blood circuit forintroducing saline and drugs (e.g., heparin) into the blood circuit. Thesaline delivery line 172 is connected to a saline bag 176. The drugdelivery line 174 is connected to a syringe 178 that contains a drug.The saline delivery line 172 is connected to the first pump line adaptor158, and the drug delivery line 174 is connected to the second pump lineadaptor 162.

The various blood lines, the saline delivery line 172, and the drugdelivery line 174 can be formed of any of various different medicalgrade materials. Examples of such materials include PVC, polyethylene,polypropylene, silicone, polyurethane, high density polyethylene, nylon,ABS, acrylic, isoplast, polyisoprene, and polycarbonate. In someimplementations, the blood component carrier body 134 is formed of PVC,polyethylene, polypropylene, polystyrene, and/or high densitypolyethylene. The various blood lines, the saline delivery line 172, andthe drug delivery line 174 are typically retained within recessedchannels formed in the carrier body 134. The recessed channels can havea diameter equal to or slightly less than the diameters of the lines sothat the lines are retained within the channels with a friction fit.Alternatively or additionally, any of various other techniques can beused to secure the lines to the carrier body 134. For example,mechanical attachment devices (e.g., clips or clamps) can be attached tothe carrier body 134 and used to retain the lines. As another example,the lines can be adhered to or thermally bonded to the carrier body 134.

Suitable blood component sets and their related components are describedin greater detail in U.S. Patent Application Publication No.2009/0101566, entitled “Dialysis Systems and Related Components,” whichis incorporated by reference herein.

FIG. 9 is an enlarged front view of the module 130 of the hemodialysismachine 102 with the door 131 of the module 130 open and the bloodcomponent set 104 removed from the module 130. As shown in FIG. 9, theblood pump 132 extends from the front face of the module 130 of thehemodialysis machine 102. The blood pump 132 is a peristaltic pump andis arranged so that the U-shaped pump line 160 extending laterally fromthe carrier body is positioned around the peristaltic pump when theblood component set 104 is secured to the front face of the module 130.

The module 130 of the hemodialysis machine 102 also includes a leveldetector 182 that aligns with the air release device 112 when the bloodcomponent set 104 is secured to the front face of the module 130. Thelevel detector 182 is adapted to detect the level of liquid (e.g., bloodand/or saline) within the air release device 112. The door 131 of themodule 130 includes a projection 183 that compresses the air releasedevice 112 against the level detector 182 when the blood component set104 is secured to the front face of the module 130 and the door 131 isclosed. The projection 183 includes a recessed region adapted to receivethe rounded exterior surface of the air release device 112. The recessedregion helps to ensure that the air release device 112 is properlypositioned with respect to the level detector 182 when the door 131 isclosed. The level detector 182 is a cylindrical member having arelatively soft tip (e.g., a sponge tip) that contacts the outer surfaceof the air release device 112 when the door 131 presses the air releasedevice 112 against the level detector 182. The tip of the level detector182 includes an ultrasound signal transmitter and receiver fordetermining the level of liquid in the air release device 112. Duringuse, the transmitter emits an ultrasonic signal that reflects off of thecontents in the air release chamber 112. The reflected signal is thendetected by the receiver. The reflected signal can be used to determinethe contents in the air release chamber 116 at the level of the leveldetector 182. The receiver can, for example, be adapted to distinguishbetween liquid, air, and a combination of liquid and air (e.g., foam).As a result, the level detector 182 can detect when the blood levelwithin the chamber 116 drops due to the entry of air into the chamber116.

While the tip of the level detector 182 has been described as includinga separate transmitter and receiver, in some implementations, the leveldetector includes a transmitter/receiver that performs both functions oftransmitting and receiving.

Still referring to FIG. 9, the module 130 of the hemodialysis machine102 also includes arterial and venous pressure transducers 184, 186 thatalign with the pressure sensor capsules 154, 156 of the blood componentset 104 when the blood component set 104 is secured to the front face ofthe module 130 and the door 131 of the module 130 is closed. Thepressure transducers 184, 186 are capable of measuring the pressure ofblood flowing through the capsules 154, 156. The pressure transducers184, 186 are cylindrical members having substantially flat surfacesexposed on the front face of the module 130. The door 131 includesspring-loaded plungers 187, 189 that compress the annular rigid members155, 157 (shown in FIG. 4) of the pressure sensor capsules 154, 156between the door 131 and the front face of the module 130 when the bloodcomponent set 104 is secured to the front face of the module 130 and thedoor 131 is closed. As a result, the membranes 159, 161 (shown in FIG.4) of the pressure sensor capsules 154, 156 are pressed against thepressure transducers 184, 186 and a seal is created between theperimeter of each of the thin membranes 159, 161 and the front face ofthe module 130. The central regions of the membranes 159, 161 of thepressure sensor capsules 154, 156 contact the flat surfaces of thepressure transducers 184, 186. As the fluid pressure changes within thepressure sensor capsules 154, 156, the amount of pressure applied to thepressure transducers 184, 186 by the pressure sensor capsules 154, 156also changes. The pressure transducers 184, 186 are capable of detectingthese pressure changes during use.

An air bubble detector 188 also extends from the front face of themodule 130. When the blood component set 104 is secured to the frontface of the module 130, the venous patient line 108 passes through(e.g., is threaded through) the air bubble detector 188. The air bubbledetector 188 includes a housing that forms a channel in which the venouspatient line 108 is received. The door 131 of the module 130 includes afin 191 that presses the venous patient line 108 into the channel of thehousing and against a sensor of the air bubble detector 188 when thedoor 131 is closed. The air bubble detector 188 is capable of detectingair bubbles within the venous patient line 108. In some implementations,the air bubble detector 188 is an optical detector. The OPB 350 bubbledetector made by Optek can, for example, be used. Any of various othertypes of optical detectors can alternatively or additionally be used.Similarly, other types of sensors, such as sensors utilizing ultrasoundtechnology can be used as the air bubble detectors.

Downstream of the air bubble detector 188, the venous patient line 108passes through (e.g., is threaded through) an occluder or clamp 190.Similar to the air bubble detector 188, the occluder 190 has a housingthat forms a channel in which the venous patient line 108 is received.The door 131 of the module 130 includes a fin 193 that presses thevenous patient line 108 into the channel of the housing of the occluder190 when the door 131 is closed. The occluder 190 is configured to crimpthe portion of the venous patient line 108 disposed therein to preventblood from passing through the venous patient line 108 when activated.The occluder 190 can, for example, be connected to the air bubbledetector 188 so that the occluder 190 can be activated when the airbubble detector 188 detects an air bubble within the venous patient line108. Such an arrangement helps to ensure that no air bubbles reach thepatient in the event that the air release device 112 fails to remove oneor more air bubbles from the blood. In some implementations, theoccluder 190 is a solenoid based ram. Alternatively or additionally,other types of automated occluders can be used.

Referring briefly to FIG. 1, a drug pump 192 also extends from the frontof the hemodialysis machine 102. The drug pump 192 is a syringe pumpthat includes a clamping mechanism configured to retain the syringe 178of the blood component set 104. The drug pump 192 also includes astepper motor configured to move the plunger of the syringe 178 alongthe axis of the syringe 178. A shaft of the stepper motor is secured tothe plunger in a manner such that when the stepper motor is operated ina first direction, the shaft forces the plunger into the syringe, andwhen operated in a second direction, the shaft pulls the plunger out ofthe syringe 178. The drug pump 192 can thus be used to inject a liquiddrug (e.g., heparin) from the syringe 178 into the blood circuit via thedrug delivery line 174 during use, or to draw liquid from the bloodcircuit into the syringe 178 via the drug delivery line 174 during use.

As discussed in more detail below, as an alternative to or in additionto using a drug-containing syringe in combination with a syringe pump toinject liquid drug into the blood circuit or to draw liquid our of theblood circuit, the system can be adapted to pump liquid drug into theblood circuit from a drug vial and/or to draw liquid out of the bloodcircuit and into a vial.

The level detector 182, the pressure transducers 184, 186, the touchscreen 118, and the speaker 122 are connected to a control unit (e.g., amicroprocessor) of the hemodialysis machine 102. These devices can beconnected to the microprocessor in any manner that permits signals to betransmitted from the devices to the microprocessor and vice versa. Insome implementations, electrical wiring is used to connect themicroprocessor to the instruments. Wireless connections canalternatively or additionally be used. As described below, themicroprocessor can activate an audio and visual alarm using the speaker122 and the touch screen 118 upon receiving signals indicating that theliquid level detected by the level detector 182 is outside a desiredliquid level range and/or upon receiving signals that the pressuresensed by the pressure transducer 186 is outside a desired pressurerange. Liquid levels and pressures detected to be outside of a desiredrange, as discussed in greater detail below, can indicate that the airrelease device 112 (e.g., the vent assembly 114 of the air releasedevice 112) is not functioning properly.

Still referring to FIG. 1, the dialysate circuit is formed by multipledialysate components and dialysate lines positioned inside the housingof the hemodialysis machine 102 as well as the dialyzer 110, a dialyzerinlet line 200, and a dialyzer outlet line 202 that are positionedoutside of the housing of the hemodialysis machine 102. The dialyzerinlet line 200 includes a connector adapted to connect to one end regionof the dialyzer 110, and the dialyzer outlet line 202 includes aconnector adapted to connect to another end region of the dialyzer 110.

FIG. 10 is a schematic showing the flow paths of fluids into, through,and out of the blood circuit and the dialysate circuit of thehemodialysis system 100. Referring to the right side of FIG. 10, thedialysate components of the dialysate circuit that are located insidethe housing of the hemodialysis machine 102 include a first dialysatepump 204, a balancing device 206, a pressure sensor 208, an equalizingchamber 210, a second dialysate pump 212, and an ultrafiltration pump214. These dialysate components are fluidly connected to one another viaa series of dialysate lines 216.

The dialysate pump 204 is capable of pumping dialysate to the balancingchamber 206 via the dialysate supply line 126. In some implementations,the dialysate pump 204 is a peristaltic pump. However, any various othertypes of pumps can alternatively or additionally be used. Examples ofother suitable types of pumps include diaphragm pumps and gear pumps.

The balancing device 206 includes a spherical chamber that is dividedinto a first chamber half 218 and a second chamber half 220 by aflexible membrane 222. As fluid flows into the first chamber half 218,fluid is forced out of the second chamber half 220, and vice versa. Thisbalancing device construction helps to ensure that the volume of fluidentering the balancing device 206 is equal to the volume of fluidexiting the balancing device 206. This helps to ensure that the volumeof fresh dialysate entering the dialysate circuit is equal to the volumeof spent dialysate exiting the dialysate circuit when desired duringtreatment, as described in greater detail below.

During hemodialysis, the dialysate exiting the second chamber half 220is directed through the dialyzer 110 toward the equalizing chamber 210.The pressure sensor 208 located along the dialysate line 216 connectingthe dialyzer 110 to the equalizing chamber 210 is adapted to measure thepressure of the spent dialysate exiting the dialyzer 110. Any of variousdifferent types of pressure sensors capable of measuring the pressure ofthe spent dialysate passing from the dialyzer 110 to the equalizingchamber 210 can be used.

The spent dialysate collects in the equalizing chamber 210. Thedialysate pump 212 is configured to pump the spent dialysate from theequalizing chamber 210 to the first chamber half 218 of the balancingdevice 206. In some implementations, the dialysate pump 212 is aperistaltic pump. However, any various other types of pumps canalternatively or additionally be used. Examples of other suitable typesof pumps include diaphragm pumps and gear pumps. As the first chamberhalf 218 of the balancing device 206 fills with the spent dialysate,fresh dialysate within the second chamber half 220 is expelled towarddialyzer 110. Subsequently, as the second chamber half 220 is refilledwith fresh dialysate, the spent dialysate within the first chamber half218 is forced through the drain line 128 to the drain.

The ultrafiltration line 129 is connected to an outlet of the equalizingchamber 210. The ultrafiltration pump 214 is operatively connected tothe ultrafiltration line 129 such that when the ultrafiltration pump 214is operated, spent dialysate can be pulled from the equalizing chamber210 and directed to the drain via the ultrafiltration line 129.Operation of the ultrafiltration pump 214 while simultaneously operatingthe dialysate pump 212 causes increased vacuum pressure within thedialysate line 216 connecting the equalizing chamber 210 to the dialyzer110, and thus creates increased vacuum pressure within the dialyzer 110.As a result of this increased vacuum pressure, additional fluid ispulled from the blood circuit into the dialysate circuit across thesemi-permeable structure (e.g., semi-permeable membrane orsemi-permeable microtubes) of the dialyzer 110. In certainimplementations, the ultrafiltration pump 214 is a peristaltic pump.However, any various other types of pumps can alternatively oradditionally be used. Examples of other suitable types of pumps includediaphragm pumps and gear pumps.

Referring to FIGS. 1 and 10, a method of preparing the hemodialysissystem 100 for hemodialysis treatment will now be described. Beforehemodialysis treatment is initiated, saline is introduced from thesaline bag 176 into the blood circuit via the saline delivery line 172in order to prime the blood circuit. To draw the saline from the salinebag 176 into the blood circuit, a valve along the saline delivery line172 is opened, a valve along the dialysate supply line 126 is closed,and the blood pump 132 is turned on. The saline enters the blood circuitvia the pump line adaptor 158 (shown in FIGS. 3 and 4) and then flowsthrough the U-shaped blood line 160 that engages the blood pump 132. Theblood pump 132 forces the saline through the blood circuit toward thedialyzer 110. The saline flows through the dialyzer 110 and exits thedialyzer 110 via the dialyzer outlet line 170. As the saline flowsthrough the dialyzer outlet line 170 toward the air release device 112,the saline passes through the venous pressure sensor capsule 156. Next,the saline flows through the entry port 142 of the air release device112 and fills the chamber 116 of the air release device 112. To fill thechamber 116 completely, the venous patient line 108, which leads awayfrom the air release device 112, is clamped while the saline is forcedinto the chamber 116. If the vent assembly 114 of the air release device112 is functioning properly, air is forced out the top of the chamber116 and through the vent assembly 114 as saline fills the chamber 116.The saline does not pass through the vent assembly 114 if the ventassembly 114 is functioning properly because the membrane 148 of thevent assembly 114 is hydrophobic.

If the vent assembly 114 of the air release device 112 is notfunctioning properly, air within the blood circuit may not be allowed toescape from the chamber 116 of the air release device 112 during use.Such an improperly functioning air release device 112 might not benoticed during the priming procedure. For example, if a relatively smallvolume of air is within the blood circuit when the priming occurs, thatsmall volume of air, which would get trapped in the chamber 116 of theair release device 112, might go unnoticed by the operator of thehemodialysis system 100. Therefore, it is advantageous to test theoperability of the air release device 112 after priming and beforetreatment.

In order to test the air release device 112, the blood pump 132 isturned off, the venous patient line 108 is clamped, and theultrafiltration pump 214 is started. Because the blood pump 132 isturned off, the blood pump 132 acts as a closed clamp on the arterialpatient line 106. Therefore, the blood circuit acts as a substantiallyclosed fluid circuit with the vent assembly 114 of the air releasedevice 112 being the only point of entry and exit for air or othergases. The vacuum pressure created across the semi-permeable structureof the dialyzer 110 by running the ultrafiltration pump 214 causessaline to be pulled from the blood circuit to the dialysate circuit.Because the arterial and venous patient lines 106, 108 are clamped, theonly fluid access to the blood circuit is through the vent assembly 114of the air release device 112. Therefore, if the vent assembly 114 ofthe air release device 112 is functioning properly, air will be pulledacross the vent assembly 114 and into the chamber 116 of the air releasedevice 112 due to the vacuum pressure. The ultrafiltration pump 214continues to run until a sufficient vacuum is applied to the dialysatecircuit to draw enough air into the air release device 112 (assuming aproperly functioning air release device 112) to activate the leveldetector 182. In other words, the ultrafiltration pump 214 continues torun until a sufficient amount of air would be pulled through the ventassembly 114 of a properly functioning air release device 112 to causethe saline level within the air release device 112 to drop below thelevel of the level detector 182. Typically, the ultrafiltration pump 214is operated in a manner to draw a sufficient amount of air into aproperly functioning air release device to activate the level detector182 without drawing so much air into the blood circuit that the airreaches the venous patient line 108 causing the air bubble detector 188and occluder 190 to be activated.

Various different parameters affect the volume of air pulled into thechamber 116 of a properly functioning air release device 112. Forexample, the operation time of the ultrafiltration pump 214, the pumpspeed of the ultrafiltration pump 214, the permeability of the ventassembly 114 of the air release device 112, etc. dictate the volume ofair pulled into the air release device 112. In some implementations, theultrafiltration pump 214 is operated for about ten seconds to about oneminute (e.g., about 30 seconds) during the test procedure. In certainimplementations, the ultrafiltration pump is operated to pump fluid at arate of about 1 L/hr to about 4 L/hr (e.g., about 2 L/hr to about 3L/hr).

As air is drawn into the chamber 116 of the air release device 112, theliquid level within the chamber 116 drops. When the liquid level dropsbelow the level at which the level detector 182 is positioned, the leveldetector 182 will no longer detect liquid in the chamber 116 of the airrelease device 112. As a result, the level detector 182 will transmit asignal to the microprocessor, indicating the absence of liquid in theair release device 112 at the height of the level detector 182. If thelevel detector 182 detects the absence of liquid in the chamber 116 ofthe air release device 112 after running the ultrafiltration pump 214for the desired time and at the desired speed, this indicates that theair release device 112 is functioning properly. If, however, the leveldetector 182 still detects liquid in the chamber 116 of the air releasedevice 112 after running the ultrafiltration pump 214 for the desiredtime and at the desired speed, this indicates that the air releasedevice 112 is not functioning properly. The microprocessor of thehemodialysis machine 102 is configured to activate a visual and audioalarm upon receiving signals from the level detector 182 that the liquidlevel within the chamber 116 has not dropped below the level of thelevel detector 182 after operating the ultrafiltration pump 214 for thedesired time and at the desired speed. In particular, the microprocessortransmit signals to the touch screen 118 and the speaker 122, causingthe touch screen 118 to emit a visual signal and the speaker 122 to emitan audio signal. These visual and audio signals alert the operator ofthe system 100 to the possibility of a malfunctioning air release device112 (e.g., a malfunctioning vent structure 114 of the air release device112).

After determining whether the air release device 112 is functioningproperly, any air that was drawn into the air release device 112 isforced back out to the atmosphere. To do this, the ultrafiltration pump214 is turned off and the blood pump 132 is turned on. Because thevenous patient line 108 is still clamped at this time, the operation ofthe blood pump 132 builds a substantial amount of pressure within theblood circuit. This pressure forces the air within the chamber 116 ofthe air release device 112 to exit the chamber 116 via the vent assembly114 of the air release device 112.

If it was determined that the air release device 112 was not functioningproperly during the test procedure, then the air release device 112 canbe replaced or repaired. In some implementations, for example, theoperator may simply disconnect all of the blood lines and bloodcomponents of the blood component set 104 and discard that entire bloodcomponent set 104. A new blood component set 104 would then be connectedto the hemodialysis machine 102. Alternatively, the air release device112 alone could be disconnected from the carrier body 134 of the bloodcomponent set 104 and replaced with a new air release device 112. Asanother alternative, the vent assembly 114 of the malfunctioning airrelease device 112 could be removed from the air release device 112 andreplaced with a new vent assembly 114. The air release device 112 withthe new vent assembly 114 would then be reconnected to the remainder ofthe blood component set 104. After replacing or repairing the airrelease device 112, the priming and testing processes described abovewould be repeated prior to beginning hemodialysis treatment.

In some implementations, the microprocessor of the hemodialysis machine102 is adapted to disable certain functions of the hemodialysis machine102 until the operator of the system 100 indicates that themalfunctioning air release device 112 has been replaced or repaired oruntil the hemodialysis machine 102 itself is able to confirm that themalfunctioning air release device 112 has been replaced or repaired(e.g., by detecting an acceptable level of liquid within the chamber 116of the air release device 112 during a subsequent test). The functionsthat are disabled by the microprocessor can, for example, be functionsrequired to carry out hemodialysis treatment. Disabling these featurescan help to ensure that treatment is not performed using a bloodcomponent set with a malfunctioning air release device.

After priming the blood circuit and confirming that the air releasedevice 112 is functioning properly, the arterial and venous patientlines 106, 108 are connected to a patient 250, as shown in FIG. 11, andhemodialysis is initiated. During hemodialysis, blood is circulatedthrough the blood circuit (i.e., the various blood lines and bloodcomponents, including the dialyzer 110, of the blood component set 104).At the same time, dialysate is circulated through the dialysate circuit(i.e., the various dialysate lines and dialysate components, includingthe dialyzer 110).

Focusing first on the blood circuit shown on the left side of FIG. 11,during hemodialysis, the blood pump 132 is activated causing blood tocirculate through the blood circuit. The blood follows the same basicroute as the route of the saline described above and, for the most part,pushes the residual saline in the blood circuit through the variousblood components and blood lines and back to the patient. The blood isdrawn from the patient 250 via the arterial patient line 106 and flowsto the arterial pressure sensor capsule 154. The arterial pressuresensor 184 on the front face of the module 130 (shown in FIG. 9) alignswith the pressure sensor capsule 154 and measures the pressure of theblood flowing through the blood circuit on the arterial side. The bloodthen flows through the U-shaped pump line 160, which is operativelyengaged with the blood pump 132. From the pump line 160, the blood flowsto the dialyzer 110. After exiting the dialyzer 110, the blood flowsthrough the venous pressure sensor capsule 156 where the pressure of theblood on the venous side is measured by the associated pressure sensor186 on the front face of the module 130 (shown in FIG. 9).

In certain implementations, a drug, such as heparin, is injected intothe blood via the drug delivery line 174 by activating the drug pump192. Injecting heparin into the blood can help to prevent blood clotsfrom forming within the blood circuit. Other types of drugs canalternatively or additionally be injected from the syringe 178 into theblood circuit. Examples of such drugs include vitamin D and ironsupplements, such as Venofer® and Epogen®.

Next, the blood flows through the entry port 142 of the air releasedevice 112 in which any gas, such as air, in the blood can escape. Whenthe blood enters the chamber 116 of the air release device 112, theblood forces the saline at the bottom of the chamber 116, which remainsin the chamber 116 from the priming procedure, through the exit port 144of the air release device 112. However, the blood does not displace allof the saline within the chamber 116. Because of the size and shape ofthe chamber 116, the blood enters the chamber 116 and only traversespart of the height of the chamber 116 before flowing back down andexiting the exit port 144. The interface 152 (shown in FIG. 5) betweenthe saline and the blood delineates the furthest extent of the vastmajority of the blood within the chamber 116. Because blood and salineare not immiscible, there is some amount of mixing between the twofluids around the interface 152.

The saline substantially prevents the blood from contacting the membrane148 of the vent assembly 114. However, some blood can be present in thesaline without hindering treatment. That is, the saline need not becompletely free of blood for the air release device 112 to both allowgas (e.g., from air bubbles in the blood) to vent from the blood circuitand retain the liquid within the blood circuit. The solution that ismostly saline protects the membrane 148 of the vent assembly 114 frombecoming coated with protein, which could clog the vent assembly 114 andreduce the ability of the air release device 112 to vent air and othergases from the chamber 116 of the air release device 112 to theatmosphere. If the chamber 116 of the release device 112 is sufficientlyelongated, the blood does not mix with the saline at the top portion ofthe chamber 116 because the saline remains relatively stagnant as theblood flows through the chamber 116.

Any unbound gas, or air, that is in the blood, such as air that isintroduced by the dialyzer 110 or syringe 178, rises as tiny air bubbleswithin the blood and saline until the air eventually vents out throughthe vent assembly 114. The blood travels up and over the dam 146 ratherthan straight across the bottom of the chamber 116 and out the exit port144. By directing the flow of blood upwards, the blood with air is notable to flow in and directly back out of the chamber 116 without flowingupwards to at least a height greater then the height of the dam 146. Thesurface area of the dam 146 and the inner walls of the chamber 116encourage air, including microbubbles, to separate from the blood andexit the blood circuit through the vent assembly 114.

After exiting the air release device 112, the blood travels through thevenous patient line 108 and back to the patient.

Turning now to the dialysate circuit illustrated on the right side ofFIG. 11, during hemodialysis, fresh dialysate is pumped into thedialysate circuit from the dialysate container 124 via the dialysatesupply line 126 by running the dialysate pump 204. The fresh dialysateenters the second chamber half 220 of the balancing device 206. As spentdialysate enters the first chamber half 218 of the balancing device 206,the fresh dialysate is forced out of the second chamber half 220 andtoward the dialyzer 110 via the dialysate line 216. The dialysate passesthrough the dialyzer 110 at the same time that the patient's blood ispassed through the dialyzer 110 on an opposite side of thesemi-permeable structure of the dialyzer 110. As a result, toxins, suchas urea, are transferred across a permeable structure (e.g., permeablemembrane and/or permeable microtubes) of the dialyzer 110 from thepatient's blood to the dialysate, and those toxins collect in thedialysate forming spent dialysate. The spent dialysate exiting thedialyzer 110 is circulated through the dialysate circuit to theequalizing chamber 210. The dialysate pump 212 draws spent dialysatefrom the equalizing chamber 210 and delivers it to the first chamberhalf 218 of the balancing device 206. As the spent dialysate fills thefirst chamber half 218, fresh dialysate within the second chamber have220 is delivered to the dialyzer 110. As the second chamber half 220 issubsequently refilled with fresh dialysate, the spent dialysate withinthe first chamber half 218 is forced out of the balancing device 206 andinto a drain via the drain line 128. The balancing device 206 balancesthe dialysate entering the dialysate circuit with the dialysate exitingthe dialysate circuit to ensure that a substantially constant volume ofdialysate remains within the dialysate circuit when ultrafiltration isnot being performed.

In certain treatments, an ultrafiltration process is performed to removeexcess fluid from the patient's blood. During ultrafiltration, apressure gradient is created across the permeable structure between thedialysate side and the blood side of the dialyzer 110 by running theultrafiltration pump 214. As a result, fluid is drawn across thesemi-permeable structure of the dialyzer 110 from the blood circuit tothe dialysate circuit. Spent dialysate, including the toxins and excessfluid drawn from the patient, is drawn from the equalizing chamber 210by the ultrafiltration pump 214 and is delivered to the drain via theultrafiltration line 129.

It is also advantageous to periodically test the vent assembly 114 ofthe air release device 112 during the hemodialysis treatment. By doingthis, it is possible to detect damage that might occur to the ventassembly 114 during treatment. For example, such a testing procedure canbe used to detect whether the membrane 148 of the vent assembly 114 hasruptured causing liquid to contact the vent structure 150 and thuscausing the vent structure 150 to self-seal. Such a testing procedurecan also be used to detect whether protein has built up on the membrane148 of the vent assembly 114 due to contact with blood and, as a result,significantly diminished the ability of the vent assembly 114 to allowair to pass therethrough.

In order to test the air release device 112 during hemodialysistreatment, the blood pump 132 and the dialysate pumps 204, 212 aretemporarily stopped, the venous patient line 108 is clamped, theultrafiltration pump 214 is turned on, and the blood level within thechamber 116 of the air release device 112 is monitored. Typically, thetest lasts no more than about 60 seconds (e.g., no more than about 15seconds, about 10-15 seconds), and thus the blood pump 132 can bestopped without negatively affecting the blood in the blood circuit. Adrop in the blood level within the chamber 116 below the level of thelevel detector 182 after running the ultrafiltration pump 214 for adesired time and at a desired speed indicates that the vent assembly 114of the air release device 112 is functioning properly, while a drop inthe blood level to a point above the height of the level detector 182 orno drop at all in the blood level indicates that the vent assembly 114is not functioning properly. If the vent assembly 114 is determined tobe functioning properly, the treatment simply resumes. If, however, thevent assembly 114 is determined to be working improperly, the operatorof the hemodialysis system 100 is alerted via the touch screen 118 andthe speaker 122 so that remedial action can be taken. In response tosuch an alert, the operator can repair or replace the air release device112 using any of the various techniques described above. It isadvantageous for the user to be able to repair the air release device112 under these circumstances by simply replacing the vent assembly 114.This allows the user to repair the air release device 112 with only aminor interruption to the remainder of the blood circuit, which,contains blood during treatment.

In certain implementations, the above-described test procedure isautomated and is performed regularly throughout the treatment.Alternatively, the control unit of the hemodialysis machine 102 can beadapted to simply alert the user (e.g., via the touch screen 118 and/orthe speaker 122) when it is time to manually perform the test. In someimplementations, the test is performed at least two times (e.g., atleast five times) during the treatment. The test can, for example, beperformed at least every 60 minutes (e.g., every 30 minutes, every 15minutes) throughout the treatment.

After completing the patient's treatment, the dialysate within thedialysate circuit is pumped to the drain using the dialysate pump 212and/or the ultrafiltration pump 214. The blood component set 104 is thendisconnected from the module 130 of the hemodialysis machine 102 anddiscarded, and the dialysate circuit is sterilized in preparation for asubsequent treatment.

While certain embodiments have been described above, other embodimentsare possible.

While the methods described above involve using the measured liquidlevel in the air release device 112 to determine whether the ventassembly 114 of the air release device 112 is working properly, othertechniques can alternatively or additionally be used. In someimplementations, for example, the blood pressure measured by the venouspressure transducer 186 is used to determine whether the vent assembly114 is functioning properly. If the vent assembly 114 is not functioningproperly, then a desired amount of air would not be pulled into theblood circuit via the vent assembly 114 when applying vacuum pressure tothe chamber 116 of the air release device 112. As a result, the pressurewithin the blood circuit would decrease and the blood lines forming theblood circuit might start to collapse. Thus, a pressure reductiondetected at the venous pressure transducer 186 of greater than a certainvalue while drawing a vacuum on the chamber 116 of the air releasedevice 112 in the manner discussed above indicates that the ventassembly 114 of the air release device 112 is not functioning properly.In some implementations, for example, a pressure reduction of about 100mm Hg or more indicates that the vent assembly 114 is not workingproperly. A pressure drop of less than a certain value, on the otherhand, indicates that the vent assembly 114 is working properly. Incertain implementations, for example, a pressure reduction of less thanabout 10 mm Hg (e.g., about 0 mm Hg) indicates that the vent assembly114 is working properly or sufficiently.

In some implementations, the level detector 182 and the venous pressuretransducer 186 are used in combination to determine whether the ventassembly 114 of the air release device 112 is functioning properly.Thus, even if one of the level detector 182 and venous pressuretransducer 186 were not working properly, a malfunctioning vent assembly114 could still be detected. Alternatively, the control unit of thehemodialysis machine 102 can be adapted so that no alarm is activatedunless both the level detector 182 and the venous pressure transducer186 indicate that the vent assembly 114 is not functioning properly.This can help to ensure that a malfunctioning vent assembly 114 is noterroneously identified to the operator of the system 100.

While the arterial pressure sensor 184 and the corresponding arterialpressure sensor capsule 154 have been described as being arrangedupstream of the blood pump 132 to measure a pre-pump arterial pressure,they can alternatively be positioned downstream of the blood pump 132 tomeasure a post-pump arterial pressure, or an additional arterialpressure sensor and arterial pressure sensor capsule can be positioneddownstream of the blood pump 132 to measure a post-pump arterialpressure. In implementations in which a post-pump arterial pressuresensor is provided, the post-pump arterial pressure sensor can be usedinstead of or in addition to the venous pressure transducer 186 todetect whether the vent assembly 114 of the air release device 112 isfunctioning properly. For example, with the venous patient line 108clamped and the blood pump 132 turned off, the ultrafiltration pump 214can be operated to draw a vacuum on the air release device 112 and thearterial pressure sensor can monitor the pressure within the bloodcircuit. Upon detecting that the pressure within the blood circuit hasdropped below a certain level, the arterial pressure sensor can transmita signal to that effect to the microprocessor of the hemodialysismachine 102, which can activate an audio and/or visual alarm to alertthe operator of the system that the air release device 112 is notfunctioning properly. In response, the operator of the system can takeany of the various different remedial actions described above.

While some of the above methods use the pressure sensed at the venouspressure transducer 186 or the pressure sensed at an arterial pressuresensor located downstream of the blood pump 132 to determine whether thevent assembly 114 of the air release device is working properly, in someimplementations, the trans-membrane pressure (i.e., the pressuredifferential between the blood circuit and the dialysate circuit) isused to determine whether the vent assembly 114 is functioning properly.The measured trans-venous membrane can be compared with the pressureranges discussed above with respect to the venous and arterial pressuretransducers in order to determine whether the air release device 112 isventing properly.

While methods discussed above involve operating the ultrafiltration pump214 to apply vacuum pressure to the air release device 112, vacuumpressure can alternatively or additionally be applied to the air releasedevice 112 using other techniques. In certain implementations, forexample, the vacuum pressure is applied to the air release device 112 byrunning the dialysate pumps 204, 212, rather than the ultrafiltrationpump 214. In some such implementations, the dialysate pump 212 isoperated while allowing a discrete amount of fluid to exit the dialysatecircuit through the first chamber half 218 of the balancing device 206but not allowing fluid to enter the dialysate circuit via the secondchamber half 220 of the balancing device. The dialysate pump 204 remainsoff as the fluid exits the dialysate circuit to ensure that noadditional fluid is introduced into the dialysate circuit. The discreteamount of fluid that is removed from the dialysate circuit is dictatedby the volume of the balancing device 206. In some implementations, thebalancing device 206 has a volume of 30 cc such that 30 cc of fluid isremoved from the dialysate circuit during this procedure. Because fluidis removed from the dialysate circuit without being replaced, a negativepressure is created in the dialysate circuit. This negative pressure isalso applied to the blood circuit via the semi-permeable membrane of thedialyzer 110, and thus acts on the air release device 112. While thisnegative pressure is applied to the air release device 112, the airrelease device 112 can be tested in the manner described above. Aftertesting the air release device 112, the dialysate pump 204 is operated(while the dialysate pump 212 remains off) to pump additional fluid intothe dialysate circuit to restore the fluid volume of the dialysatecircuit to its original value. Because the volume of the balancingdevice 206 dictates the amount of fluid that is added to the dialysatecircuit, it can be ensured that the same amount of fluid that waspreviously removed from the dialysate circuit is now added back into thedialysate circuit.

As an alternative to controlling the amount of fluid delivered to andfrom the dialysate circuit based on the volumetric capacity of thebalancing device 206, other techniques can be used. In certainimplementations, for example, the pressure transducer 208 is used toensure that the same volume of fluid drawn from the dialysate circuit islater added back into the dialysate circuit. In such implementations,when it is time to test the air release device 112 by applying negativepressure to the blood circuit, a reading of the pressure transducer 208is taken. This pressure reading corresponds to the total volume of fluidwithin the dialysate circuit at that time. Then, the dialysate pump 212is operated (with the dialysate pump 204 turned off) to remove fluidfrom the dialysate circuit. While doing this, the valves associated withthe balancing device 206 are controlled in a manner to allow fluid toreadily flow through the first chamber half 218 of the balancing device206 while preventing fluid from flowing through the second chamber half220 of the balancing device 206. The removal of fluid from the dialysatecircuit causes a pressure drop within the dialysate and blood circuits,which allows the air release device 112 to be tested in the mannerdescribed above. After testing the air release device 112, the dialysatepump 204 is turned on and the dialysate pump 212 is turned off. Inaddition, the valves associated with the balancing device 206 arecontrolled in a manner to allow fluid to readily flow through the secondchamber half 220 of the balancing device 206 while preventing fluid fromflowing through the first chamber half 218 of the balancing device 206.The dialysate pump 204 continues to run until the reading of thepressure transducer 208 is the same as the reading taken before thefluid was removed from the dialysate circuit. The identical pressurereadings indicate that the total volume of fluid in the dialysatecircuit is equal to the total volume of fluid that was present in thedialysate circuit prior to removing fluid from the dialysate circuit.Because the amount of volume removed from and added back into thedialysate circuit is not limited to the volumetric capacity of thebalancing device 206 using this technique, larger volumes of fluid canbe removed from the dialysate circuit, thereby resulting in the abilityto apply increased levels of negative pressure to the air release device112.

In some implementations, the drug pump 192 is used to draw a vacuum onthe chamber 116 of the air release device 112. The drug pump 192 isoperated in a manner to draw liquid out of the blood circuit rather thanbeing operated in a manner to inject liquid (e.g., drug from the syringe178) into the blood circuit. To do this, the drug pump 192 is simply runin the opposite direction than it is run to deliver drug to the bloodcircuit. Prior to performing the test procedure, the syringe 178containing the liquid drug is replaced with an empty syringe such thatthe liquid pulled out of the blood circuit can be collected in the emptysyringe. To test the vent assembly 114 of the air release device 112,the blood pump 132, the dialysate pumps 204, 212, and theultrafiltration pump 214 are turned off, the venous patient line 108 isclamped, and the drug pump 192 is operated in a manner to pull liquidfrom the blood circuit into the empty syringe. Because the blood pump132 is stopped thereby acting as a closed clamp along the arterialpatient line 106 and the venous patient line 108 is clamped the syringepump 192 applies a vacuum pressure to the chamber 116 of the air releasedevice 112 as it pulls liquid into the empty syringe.

In certain implementations, the blood pump 132 is operated in a mannerto apply vacuum pressure to the air release device 112. In particular,rather than running the blood pump 132 in a forward direction such thatliquid within the blood circuit is pumped in the direction from thearterial patient line 106 toward the dialyzer 110, the blood pump 132 isoperated in a reverse direction such that liquid within the bloodcircuit is pumped in the direction from the dialyzer 110 toward thearterial patient line 106. To draw a vacuum on the air release device112 while operating the blood pump 132 in the reverse direction, thevenous patient line 108 is clamped and the various pumps of thedialysate circuit are turned off. As a result, when the blood pump 132is operated in the reverse direction, liquid is pulled from the chamber116 of the air release device 112 toward the dialyzer 110 and the bloodpump 132. Because the venous patient line 108 is clamped, the causes avacuum to be drawn on the chamber 116 of the air release device 112 andcan thus be used to test the functionality of the vent assembly 114 ofthe air release device 112 using any of the various techniques describedherein.

While certain methods discussed above involve clamping the venouspatient line 108 to pull a vacuum on the chamber 116 of the air releasedevice 112, the patient's arm to which the arterial and venous patientlines 106, 108 can alternatively be lowered during the test procedure.Lowering the patient's arm would decrease venous pressure and couldachieve a result similar to clamping the venous patient line 108.

While some of the above methods have been described as temporarilyhalting the flow of liquid through the blood circuit or a portion of theblood circuit while operating one of the pumps connected to thedialysate circuit to draw a vacuum on the chamber 116 of the air releasedevice 112, in some implementations, the flow of liquid through theblood circuit is maintained. In such implementations, the pump(s)connected to the dialysate circuit that are used to draw the vacuum(e.g., the dialysate pumps 204, 212 or the ultrafiltration pump 214) aresimply operated at a high enough rate to draw a vacuum on the bloodcircuit notwithstanding the flow of liquid through the blood circuit.Similarly, for those methods above that describe halting the flow ofliquid through the dialysate circuit while the blood pump 132 or thedrug pump 192 are operated in reverse to pull a vacuum on the chamber116 of the air release device 112, it should be appreciated that theflow of liquid through the dialysate circuit need not be stopped. Insuch cases, the flow of liquid through the dialysate circuit wouldincrease the vacuum pressure applied to the chamber 116 of the airrelease device 112.

While certain methods above involve forcing air out of the chamber 116of the air release device 112 by running the blood pump 132 with thevenous patient line 108 clamped, other techniques can alternatively oradditionally be used to force air out of the air release device 112. Forexample, in those implementations in which the drug pump 192 is operatedin reverse to pull a vacuum on the chamber of the air release device112, the syringe pump could subsequently be operated in the normaldirection with the venous patient line 108 clamped. This would cause anyliquid drawn into the syringe by running the drug pump 192 in reverse tobe forced back into the blood circuit and would create a positivepressure within the blood circuit. As a result, any air within thechamber 116 of the air release device 112 would be expelled to theatmosphere via the vent assembly 114. As another example, the dialysatepumps 202, 214 and/or the ultrafiltration pump 214 can be operated inreverse with the venous patient line 108 clamped in order to create apositive pressure within the blood circuit and force any air within thechamber 116 of the air release device 112 to the atmosphere via the ventassembly 114.

While the methods described above involve activating an audio alarm andvisual arm in response to detecting a malfunctioning device, an audioalarm alone or a visual alarm alone can alternatively be used to alertthe operator of the system to the malfunctioning device.

While certain visual alarms have been described as being displayed viathe touch screen 118, the visual alarms can be displayed using othertypes of devices. For example, in implementations in which the dialysismachine includes a traditional screen (i.e., a non-touch screen) alongwith a separate device, such as a keyboard, for inputting data, thevisual alarm can be displayed via the traditional screen.

While the level detector 182 has been described as an ultrasonic deviceconfigured to emit and receive ultrasonic signals, any of various othertypes of devices capable of detecting a level of liquid within thechamber 116 of the air release device 112 can be used. Examples of suchdevices include, among other things, light sensors.

While the module 130 has been described as including pressuretransducers 184, 186 to detect fluid pressure within the blood circuit,any of various other types of pressure sensors can be used to measurethis fluid pressure. In some implementations, for example, inlinepressure transducers configured to measure positive and negativepressure on the line itself may be used.

While the drug pump 192 has been described as a syringe pump, othertypes of drug pumps can be used. In certain implementations, forexample, the drug pump is a peristaltic pump. During use of such aperistaltic pump, a drug delivery line of a blood component set isconnected to a drug vial (e.g., a heparin vial) and operativelypositioned within a housing of the pump in a manner such that rollingmembers of the pump operatively engage the drug delivery line. The pumpcan be operated in a first direction to inject the drug into the bloodpassing through the blood lines of the blood component set.Alternatively, the drug delivery line can be connected to an empty vialor a drain and the pump can be operated in an opposite direction to drawliquid passing through the blood lines into the vial or drain via thedrug delivery line.

While the vent assembly 114 of the air release device 112 has beendescribed as including the membrane 148 and vent structure 150, othertypes of vents can be used. In some implementations, for example, thevent of the air release device includes only the membrane.

In some implementations, the air release device 112 and at least one ofthe other blood components and blood lines (e.g., all of the other bloodcomponents and blood lines) are incorporated into an integrated bloodcomponent set. The various components of the integrated blood circuitcan be formed together in one assembly or integrated molding rather thandiscrete separate or modular devices. The integrated blood component setcan be adapted to removably seat into the module 130 of the hemodialysismachine 102 in a manner similar to the blood component set 104 describedabove.

While the various blood components have been described as being eithersecured to the carrier body 134 or incorporated into an integrated bloodcomponent set, the blood components can alternatively be connected toone another by blood lines alone. In such implementations, the bloodcomponents would be individually secured to the hemodialysis machine 102(e.g., the module 130 of the hemodialysis machine 102) prior totreatment. The functionality of the blood components would be similar tothe functionality of those blood components discussed above.

While the dialysate circuit has been described as being partiallyintegrated with the hemodialysis machine 102, the dialysate circuit canalternatively be formed by a dialysate component set that can beremovably secured to a hemodialysis machine during use. In someimplementations, the dialysate component set is in the form of acassette that can be inserted into a drawer of the hemodialysis machinein a manner such that the cassette operatively engages components of thehemodialysis machine when the drawer is closed. Such a dialysatecomponent sets is described, for example, in U.S. Patent Application No.61/231,220, entitled “Dialysis Systems, Components, and Methods” andfiled on Aug. 4, 2009, which is incorporated by reference herein.

While the hemodialysis machine 102 has been described as including atouch screen, it should be appreciated that any of the hemodialysismachines described herein can alternatively be provided with aconventional screen and an associated control panel or keyboard to allowthe user to input data. Alternatively or additionally, the hemodialysismachine can be equipped with a scratch pad and/or touch buttons thatpermit the user to input data.

While the various instruments that the cooperate with the bloodcomponents and blood lines to cause blood flow and monitor blood flowthrough the blood circuit has been described as being part of a moduleof the hemodialysis machine, it should be appreciated that theseinstruments could be integrated into the hemodialysis machine.

While the test methods described above have been discussed with respectto air release devices in hemodialysis systems, similar methods can beused to test other types of devices that include vents to allow airand/or other gases to enter and/or exit the devices. FIG. 12, forexample, is a schematic of a hemodialysis system 302 that includes ahemodialysis machine 302 to which a blood component set including apre-pump arterial pressure sensor assembly 320, a post-pump arterialpressure sensor assembly 320′, and a venous pressure sensor assembly 420is connected. Each of the pressure sensor assemblies 320, 320′, 420includes a fluid line including a pressure transducer protector 340,340′, 440. The pressure sensor assemblies 320, 320′, 420 includepressure transducers 330, 330′, 430 that are secured to the hemodialysismachine 302. Each of the transducer protectors 340, 340′, 440 includes abody that forms a fluid pathway and a vent assembly positioned along thefluid pathway. This arrangement allows gas (e.g., air) to pass throughthe vent assemblies of the transducer protectors 340, 340′, 440, whileinhibiting the passage of blood therethrough. As a result, the pressuretransducers 330, 330′, 430 do not come into contact with blood duringtreatment. The pressure transducers 330, 330′, 430 measure changes inair pressure, which can be used to determine the pressure of the bloodwithin the blood circuit.

The vent assemblies of the transducer protectors 340, 340′, 440 help toprotect the pressure transducers 330, 330′, 430, and the dialysismachine 302 on which those transducers are mounted, from direct contactwith blood flowing within the blood circuit. Vent assemblies similar tothose discussed herein with respect to the air release devices can beused in the transducer protectors 340, 340′, 440. In someimplementations, each of the vent assemblies includes a microporousmembrane (similar to the membrane 148 described above) and aself-sealing vent structure (similar to the vent structure 150 describedabove) that is positioned between the microporous membrane and thepressure transducer 330, 330′, 430 and is designed to automatically sealshut upon coming into contact with blood. Thus, should the microporousmembrane rupture and allow blood to pass therethrough, the ventstructure will seal and will thus inhibit (e.g., prevent) the dialysismachine 302 from becoming contaminated.

During hemodialysis, blood flows from the patient 250 through thearterial patient line 106 to a drip chamber 315. Blood drips into thedrip chamber 315 where a connecting tube from the drip chamber 315connects to the hemodialysis machine 302 via the pre-pump arterialpressure sensor assembly 320. The blood pump 132 is used to pump theblood from the drip chamber 315 to the dialyzer 110. The post-pumparterial pressure assembly 320′ is connected to the blood line leadingfrom the blood pump 132 to the dialyzer 110. The pre-pump arterialpressure sensor assembly 320 and post-pump arterial pressure sensorassembly 320′ are used to determine the pressure of the blood on thearterial side of the blood circuit. After passing through the dialyzer110, the blood flows to the air release device 112 in which gas (e.g.,air) in the blood can escape before the blood continues to the patient250. The venous pressure sensor assembly 420 is connected to the bloodline leading from the dialyzer 110 to the air release device 110. Thevenous pressure sensor assembly 420 is used to determine the pressure ofthe blood on the venous side of the blood circuit. After leaving the airrelease device 110, the blood travels through the venous patient line108 and back to the patient 250.

It is beneficial to test the functionality of the vent assemblies of thetransducer protectors 340, 340′, 440 before treatment begins (e.g.,right after priming the blood circuit) and/or during treatment. Todetermine whether the vent assemblies of the transducer protectors 340,340′, 440 are functioning properly, methods similar to those discussedabove can be used.

To test the vent assemblies of the transducer protectors 340′, 440, thepressure sensor assembly 320′, 420 including the transducer protector340′, 440 to be tested is disconnected from the dialysis machine 302 anda vacuum pressure is applied to the transducer protector 340′, 440 to betested. While applying vacuum pressure to the transducer protector 340′,440 being tested, the pressure within the blood circuit is monitored bythe other of the pressure sensor assemblies 320′, 420, which remainsconnected to the dialysis machine 302, to determine whether air is beingpulled through the vent assembly as a result of the vacuum pressure. Ifair is being pulled through the vent assembly, the pressure within theblood circuit, as detected by the pressure transducer 330′, 430 of theconnected pressure sensor assembly 320′, 420, will remain within adesired pressure range and this will indicate that the vent assembly isfunctioning properly. If air is not being pulled through the ventassembly, the pressure within the blood circuit will drop below aminimum desired pressure and this will indicate that the vent assemblyis not functioning properly.

Any of the various vacuum generating techniques described above can beused to apply vacuum pressure to the transducer protectors 340′, 440.For example, the blood pump 132 can be turned off, the venous patientline 108 or the line connecting the dialyzer 110 to the air releasedevice 112 can be clamped off, and the ultrafiltration pump and/ordialysate pumps in the dialysate circuit can be operated to draw fluidfrom the blood circuit to the dialysate circuit and thus create vacuumpressure within the portion of the blood circuit between the blood pump132 and the clamp. Alternatively or additionally, the blood pump 132and/or the drug pump can be operated in reverse while the venous patientline 108 or the line connecting the dialyzer 110 to the air releasedevice 112 is clamped.

To test the vent assembly of the transducer protector 340, a vacuumpressure is applied to the transducer protector 340 by clamping thearterial patient line 106 and operating the blood pump 132 to draw fluidout of the drip chamber 315 toward the blood pump 132. At the same time,a level detector on the hemodialysis machine is used to detect theliquid level within the drip camber 315. The level detector and the dripchamber 315 can, for example, be arranged in a manner similar to thelevel detector 182 and the air release device 112. If air is beingpulled through the vent assembly of the transducer protector 340, theliquid level within the drip chamber 315 will drop below the height ofthe level detector. This will indicate that the vent assembly isfunctioning properly. If air is not being pulled through the ventassembly, the liquid level within the drip chamber 315 will remain at orabove the height of the level detector. This will indicate that the ventassembly is not functioning properly.

While the above testing methods have been described with respect tohemodialysis systems, similar methods can be used to test vented devicesof any of various other types of systems, including peritoneal dialysissystems, blood transfusion systems, cardiopulmonary bypass systems, druginfusion systems, etc.

Other embodiments are within the scope of the following claims.

1-51. (canceled)
 52. A dialysis system, comprising: an air releasedevice comprising a vent; a level detector configured to detect a levelof fluid within the air release device; and a control unit connected tothe level detector, wherein the control unit is configured to determinewhether the air release device is functioning properly based on adetected fluid level within the air release device when vacuum pressureis applied to the air release device.
 53. A dialysis system, comprising:an air release device comprising a vent; a fluid line fluidly connectedto the air release device; a pressure sensor configured to measurepressure of fluid within the fluid line; and a control unit connected tothe pressure sensor, wherein the control unit is configured to determinewhether the air release device is functioning properly based on ameasured pressure of fluid within the fluid line when vacuum pressure isapplied to the air release device.
 54. The dialysis system of claim 52,wherein: the air release device comprises a housing defining a liquidchamber, and the vent is disposed at an end of the liquid chamber. 55.The dialysis system of claim 54, wherein control unit is configured todetermine whether the vent of the air release device is functioningproperly based on determining whether air is being drawn into the liquidchamber through the vent.
 56. The dialysis system of claim 52, whereinthe level detector comprises a transmitter configured to emit ultrasonicsignals and a receiver adapted to receive ultrasonic signals.
 57. Thedialysis system of claim 52, further comprising: first and second fluidlines connected to the air release device, and a pump configured tocirculate fluid from the first fluid line to the air release device tothe second fluid line during dialysis treatment.
 58. The dialysis systemof claim 57, wherein the control unit is configured close off the secondfluid line and operate the pump in a manner to circulate fluid from thesecond fluid line to the air release device to the first fluid line toapply the vacuum pressure to the air release device.
 59. The dialysissystem of claim 57, wherein the pump is a drug pump configured tointroduce fluid into the first fluid line when operated in a firstdirection and is configured to draw fluid out of the first fluid linewhen operated in a second direction.
 60. The dialysis system of claim59, wherein the control unit is configured to operate the pump in thesecond direction to apply the vacuum pressure to the air release device.61. The dialysis system of claim 52, further comprising: a dialyzerfluidly connected to the air release device, a first fluid lineconnecting a first pump to the dialyzer, and a second fluid lineconnecting a second pump to the dialyzer, wherein the first pump isconfigured to circulate a first fluid from the first fluid line throughthe dialyzer during dialysis treatment, and wherein the second pump isconfigured to circulate a second fluid from the dialyzer through thesecond fluid line during the dialysis treatment.
 62. The dialysis systemof claim 61, wherein the control unit is configured to stop the firstpump to close off the first fluid line and operate the second pump in amanner to circulate fluid from the second fluid line to the dialyzer toapply the vacuum pressure to the air release device.
 63. The dialysissystem of claim 53, wherein: the air release device comprises a housingdefining a liquid chamber, and the vent is disposed at an end of theliquid chamber.
 64. The dialysis system of claim 63, wherein controlunit is configured to determine whether the vent of the air releasedevice is functioning properly based on determining whether air is beingdrawn into the liquid chamber through the vent.
 65. The dialysis systemof claim 53, wherein the pressure sensor comprises a pressuretransducer.
 66. The dialysis system of claim 53, wherein the fluid lineis a first fluid line connected to the air release device, and thedialysis system further comprises: a second fluid line connected to theair release device, and a pump configured to circulate fluid from thefirst fluid line to the air release device to the second fluid lineduring dialysis treatment.
 67. The dialysis system of claim 66, whereinthe control unit is configured close off the second fluid line andoperate the pump in a manner to circulate fluid from the second fluidline to the air release device to the first fluid line to apply thevacuum pressure to the air release device.
 68. The dialysis system ofclaim 66, wherein the pump is a drug pump configured to introduce fluidinto the first fluid line when operated in a first direction and isconfigured to draw fluid out of the first fluid line when operated in asecond direction.
 69. The dialysis system of claim 68, wherein thecontrol unit is configured to operate the pump in the second directionto apply the vacuum pressure to the air release device.
 70. The dialysissystem of claim 53, further comprising: a dialyzer fluidly connected tothe air release device, a first fluid line connecting a first pump tothe dialyzer, and a second fluid line connecting a second pump to thedialyzer, wherein the first pump is configured to circulate a firstfluid from the first fluid line through the dialyzer during dialysistreatment, and wherein the second pump is configured to circulate asecond fluid from the dialyzer through the second fluid line during thedialysis treatment.
 71. The dialysis system of claim 70, wherein thecontrol unit is configured to stop the first pump to close off the firstfluid line and operate the second pump in a manner to circulate fluidfrom the second fluid line to the dialyzer to apply the vacuum pressureto the air release device.